What does Acts 11:8 mean?

Peter is with the church leaders in Jerusalem, defending himself against charges that he ate with uncircumcised men—Gentiles. The charges are true, but there are extenuating circumstances.

Peter had been in Joppa, now called Jaffa, praying on the rooftop of a tanner named Simon. He fell into a trance and watched as a sheet filled with different kinds of animals lowered from heaven. Some of the animals were carnivores and reptiles, which are forbidden for Jews as food. A voice told him, "Rise, Peter; kill and eat" (Acts 10:13). Peter refused. He had never eaten any food that violated the laws given in Deuteronomy 14 and Leviticus 11, and he had no intention of starting (Acts 10:9–16).

"Common" comes from the Greek root word koinos. As Peter uses the term, it means something crass, low class, or unrefined. It's also used for anything that hasn't been dedicated for use in worshiping God. "Unclean" is from the Greek root word akathartos. Things that are unclean do not adhere to the Levitical law; in the case of food, they aren't kosher. "Unclean" doesn't mean sinful; many unpreventable physical conditions made a person unclean. But since the Babylonians took the Jews into exile and then Antiochus Epiphanes tried to destroy Judaism and Jewish culture, the Jews became very careful about obeying the Mosaic law. Even though Peter follows Jesus, he's still a Jew.